Previously, when producing a packing box from paperboard or corrugated board, paperboard or corrugated board is cut into a desired shape with a punch die to form a blank. In the process of blanking a packing box, a cutting blade 103 and a fold pressure-engraving member 104 for forming a fold without use of a cutting edge are attached to an upper die 101 of a punch die 100 as shown in FIG. 9 in order to blank a desired shape from a sheet material while forming a fold or kerf in the blank. Affixed to a lower die 102 opposed to the upper die 101 is a fold formation tape 110 which is made of fiber and provided at a position corresponding to the fold pressure-engraving member 104 in order to engrave a fold with pressure.
As illustrated in FIG. 11, in the fold formation tape 110, a fold formation groove 111 is defined by two flat groove formation members 112 which are opposed to each other with a specified spacing and each of which has an inclined face at one side thereof. In this fold formation tape 110, the rear faces of the groove formation members 112 are each provided with a pressure-sensitive adhesive layer 114 the surface of which is covered with release coated paper 113. Before use of the fold formation tape 110, an attachment aid strip 115 is temporarily fit to the fold formation groove 111. The attachment aid strip 115 has a setting groove 116 that helps attachment of the fold formation tape 110 to the board face of the lower die 102 by use of the fold pressure-engraving member 104. Generally, the fold pressure-engraving member 104 provided in the upper die 101 of the punch die 100 is fitted into the setting groove 116 to thereby retain the fold formation tape 110 with the upper die 101 (as indicated by dashed two dotted line in FIG. 9). Then, the release coated paper 113 is peeled off the rear face of the fold formation tape 110 to expose the pressure-sensitive adhesive layer 114 and, in this condition, the fold formation tape 110 is pressed against the board face of the lower die 102 and affixed thereto. In the process of punching a sheet material, the fold pressure-engraving member 104 becomes registered with the center line of the fold formation groove 111 of the fold formation tape 110 so that accurate pressure engraving of a fold becomes possible. After the fold formation tape 110 is fixedly placed in a correct position on the board face of the lower die 102, the attachment aid strip 115 that allows the fold pressure-engraving member 104 to temporarily retain the fold formation tape 110 is detached together with a bond tape 117. Thereafter, the fold formation groove 111 on the board face of the lower die 102 appears.
Generally, in the case of a packing box formed by punching, there are many places where folds intersect (i.e., fold intersection areas), depending on the shape of the blank. In this case, the fold formation tapes 110 are affixed to the board face of the lower die so as not to overlap each other in the fold intersection areas. Specifically, an end 110a of each fold formation tape 110 is obliquely cut so as to make a sharp-pointed end as shown in FIG. 10 and the fold formation tapes 110 are affixed to the board face with their sharp-pointed ends in butting contact with each other. If the cut fold formation tapes 110 are used as they are in the fold intersection areas, the edges of the cut end will vertically project, thrusting into the surfaces of the blank when a fold is formed and, as a result, the blank surfaces will be hurt. To avoid this, post treatment (chamfering) is applied to the fold formation tapes to obliquely cut down the angular side edges 118 to thereby remove the projecting points.
Such chamfering treatment has heretofore been manually carried out by use of a cutter knife or the like. However, the manual processing of a large number of fold formation tapes requires a lot of labor and therefore is inefficient. Recently, there have been proposed chamfering techniques that utilize a machine and some of them have come into practical use (see Patent Documents 1 to 3).
Patent Document 1: JP-A-2000-135746
Patent Document 2: JP-A-2003-165166
Patent Document 3: JP-A-2005-193523
In the technique disclosed in Patent Document 1, a workpiece material to be chamfered (that is referred to as “supported grooved member” in the specification) is placed on a member supporting table such that it can be compressed from above and below. An end of the workpiece material is tilted at a specified angle relative to a rotary cutter and the side faces of one end are cut one by one, thereby chamfering the workpiece material. This technique has accordingly revealed the disadvantage that the workpiece material has to change its position at least twice for chamfer processing, which takes a lot of time and labor. In addition, the length of the workpiece material to be used must be determined in accordance with its use position and therefore the workpiece material cut into a specified length needs to be chamfered at both ends. That is, the workpiece material has to be turned around and chamfered twice at each end. And, the angle of the workpiece material has to be adjusted whenever the position of the workpiece is changed. Such a chamfering process leads to poor operational efficiency. Moreover, the apparatus for carrying out such a process is complicated in structure and difficult to handle.
The apparatus disclosed in Patent Document 2 is designed to individually cut the ends of a fold formation member (workpiece material) by use of two cutting devices. After the fold formation member is fixedly placed on a fixing table, the fixing table is rotated through a specified angle in a direction toward the cutting devices located at a side of the fixing table and then fixed. Thereafter, the associated cutting device is operated to cut one end of the fold formation member with a cutting blade. Accordingly, the fixing table on which the fold formation member is mounted is required to be turned around twice in this apparatus. Such turning operation sounds simple but is actually troublesome. In addition, the ends of the fold formation member are processed one by one so that the apparatus of Patent Document 2 exhibits poor workability similarly to Patent Document 1.
Patent Document 3 discloses a ruled line formation tape end cutting apparatus configured to chamfer both side faces of the ends of a workpiece tape placed on a support table by centering with a pair of rotary cutters having a hat-shaped cutter face. The workpiece tape is preliminarily cut such that its ends have an acute angle. Since the apparatus of the above structure carries out chamfer finishing by cutting both sides of the ends of a workpiece tape, which has been cut to have acute-angled ends, at a time with the rotary cutters, it seems to be more efficient compared to the prior art techniques described earlier. However, this apparatus poses a security risk because the rotating cutters come in proximity to the operator's hands when setting a workpiece tape in the processing section. If the rotation of the cutters is stopped each time a workpiece tape is set, the workability of the apparatus will decrease. Therefore, the operator is required to set a workpiece while continuing the operation of the apparatus. This setting operation is performed in a narrow space and therefore highly risky.